This invention relates to articulated railroad cars having a plurality of car units articulated to one another and used for transporting truck trailers or containers.
The present invention relates to so-called articulated "spine" car units which have minimum structure such as a central beam or spine, and which are constructed with end car units having standard trucks and standard couplers for coupling with other cars in a train makeup, and which have interior car units sharing a common truck with adjacent, end car units. An articulated connector is mounted on each shared truck to provide an articulated movement between adjacent car units as the car travels about a curve. Typically, such an articulated railroad car has five car units with three interior car units and four shared trucks; and the car units may be readily converted to support either truck trailers or containers, as disclosed in U.S. Pat. Nos. 5,052,868 and 4,233,909.
In some countries, for example, European countries, these articulated cars have not met with the widespread success that they enjoy in countries such as the United States. It is thought that one reason for this lack of success is that these articulated cars often would have axle weight loads on a shared truck in excess of the per axle weight load limit, e.g., an axle load limit of 22.5 metric tonnes in a typical European country. In the United States, the axle weight load limit for a shared truck is a higher limit of 39 metric tonnes per axle, because of the stronger road beds in the United States.
In the United States, a well car is often used to transport containers with two containers being stacked one on the other. The well car has a deep well positioned intermediate the trucks at the ends of the car and positioned downwards, significantly below the top of the trucks. Even with this depressed well, in some instances, and very often in countries outside the United States and particularly in Europe, tunnels do not have height to provide clearance for a second, upper stacked container; and only a single container can be placed in the well car. In such instances, the well cars lose one-half of their efficiency in handling freight. In the conventional spine, flat cars, truck trailers also may sit too high, for example, about 16 feet from the tracks, and this is over the thirteen to fourteen foot height limit to have the proper clearance to pass through many tunnels in Europe and other countries although they will operate in the United States.
From an expense standpoint, the articulated car has fewer trucks in that the interior car units share a common truck, and the interior car units lack the expensive semi-automatic couplers or cushioning devices that are only provided for the end car units. The spine cars also have a minimal amount of parts compared to conventional flat cars making them lightweight as well as less expensive. Despite these cost advantages, the spine car has not been widely adopted in Europe because it is thought the height limitation precludes carrying of trailers, and that the carrying of trailers will result in excessive loads on the axles of the interior car units.